The submarine is to be generic, so could be shown in use by either side - for story line posts or game posts (attack on submarine in dock ...)
Off to the scraps box (card, sprue and plasticard) to make a conning tower and simple deck gun, shown here with some 1/72 figs.
I marked out a base hull outline on some 3mm MDF and cut it out, trying out the placement of the conning tower and deck gun.
Overall length is 20", a smaller one used for coastal actions.








